Various quaternary ammonium compounds are known in the art to possess fabric softening properties. These quaternary ammonium compounds, and other cationic fabric softening compounds are also known to be generally incompatible with anionic surfactants commonly employed in laundering compositions. The anionic surfactants attack and inactivate the quaternary ammonium compounds in the wash water environment. Thus larger amounts than desired of the fairly expensive quaternary ammonium compounds must be added to detergent compositions to provide a softening effect but this would result in total inactivation of the anionic active. For this reason, detergent compositions containing both anionic surfactants and cationic fabric softeners have not been commercially successful.
Previous proposals on this subject have repeatedly put forward the hypothesis that, in order to avoid inactivation of the cationic fabric softening compounds it is necessary to prevent these cationic materials from dispersing in the wash liquor.
Thus U.S. Pat. No. 2, 936,537 (Baskerville) teaches the mixing of quaternary ammonium compounds with organic dispersion inhibitors into particles. U.S. Pat. No. 4,141,841 (McDanald) teaches that such particles may be agglomerated with water-soluble neutral or alkaline salts. European patent application EP 1315 (Procter & Gamble) teaches that particles of a cationic softener and a dispersion inhibitor can be embedded in spray dried granules of anionic surfactant and builder.
The solutions proposed above have not proved suitable for line-dried fabrics.